Decomposition of refractory alkali-metal-bearing and aluminiferous minerals.



WAITSTILL H. SWENARTON, 0F MON'IGLAIR, NEW JERSEY.

DECOMPOSITION 0F REFRACTORY -.ALKALI-METAL-BEARING AND MINERALS.

N 0 Drawing.

To all whom it may-concern:

Be it known that I, VVAITSTILL I-I. SWEN ARToN,-of Montclair, in the county of Essex and State of New Jersey, have invented new and useful Improvements in Decomposition of Refractory Alkali Metal-Bearing and Aluminiferous Minerals, of which the following is a specification.

This invention relates to, decomposition of refractory minerals, and particularly aluminiferous alkali metal silicates, such as feldspar, and aluminum compounds producible therefrom, such as alum, aluminum chloridand the like,

In the production of potash from native minerals such as orthoclase, i. 6., potashfeldspar (which approximates the formula KAlSi .,O,), and from alunite, (which closely resembles potash alum in composirtion, -'but contains a relatively larger proportion of alumina than common potash alum) it is essential that the utmost economy be practised in such processing thereof in order to render it possible to profitably obtain the potash (K 0) and aluminum compounds in an available condition therefrom. In fact when Working on the requisite scale, which is required to obtain substantial quantities of potash for commercial purposes, the byproducts are produced in enormous quantities and by various methods which have been heretofore proposed many of such by-prodncts are practically worthless, owing to the fact that such enormous amounts of the same are produced which amounts are far in excess of the entire consumptive demand therefor.

My invention has for its objects the simplification of the process of decomposing such minerals and the reduction of the number of by-products so obtained to a minimum amount, as wellas the recovery, as far as possible, of the materials employed for reuse in subsequent operations.

As applied to alkali bearing silicates such as potash-feldspar or orthoclase, my process is carried out as follows One hundred parts of finely pulverized potash feldspar (preferably ground to 150 to 200 mesh), containing preferably about 14% or more of potash (K 0), is intimately mixed with 100 parts of finely powdered pearl-ash, (2'. e., potassium carbonate), and then fused in a. suitable furnace. The foregoing proportions are based upon 100% Specification of Letters Patent.

Patented Sept. 3, 1918.

Application filed March 23, 1912. Serial No. 685,840.

potassium carbonate and obviously if the carbonate employed is of a lower degree of purity, a correspondingly increasedquantity is employed, although it is notfabsolutely essential to ,employ the aforesaid quantity. Preferably the temperatureof the material is maintained just high enough, preferably between brilliant red (800 C.) and bright orange (1200 C.) heat, to maintain the mixture in a state of fusion ,or incipient fusion for a sufiicient length of time to complete the necessary reaction between the feldspar and the flux employed, for example, 5} to 1%; hours. The converted mass is then ALUMINIEEROUS I removed from the furnace, preferably pub 70 verized to about 7 5 mesh size, and then digested with approximately ten volumes of water, preferably hot" water maintained at or near the boiling point. I

After digesting with water as aforesaid, the mass is preferably actively boiled until noticeable decomposition occurs, and the mass is broken down into what is believed to be normal acid-soluble, double, potassium aluminum silicate and a solution consisting of the original potash solution and the surplus silica originally existing in the feldspar. Whether this is .the actual reaction which occurs is unimportant, but the heating should preferably be continued until the mass is thoroughly disintegrated andhas become completely decomposed by the alkali present to the greatest extent it is capable of. This decomposition into an acidsoluble double silicate is indicated by the sudden swelling and thickening of the precipitate, and its suspension throughout the entire body of the liquid as distinguished from the heavy sediment originally introduced into the digesting water. In order to reduce to a minimum the amount of acid, required to subsequentlyv decompose the compound obtained bly such violent boiling, which is preferably continued for a period of 30 minutes, the mixture is then filtered, and thereby it is possible to recover a large portion, if not all the original flux in a caustic state. Any silica dissolved therein is .then precipitated therefrom by concentrating and then carbonatin-g the filtrate so obtained until a suitable test-indicates that no more precipitate forms and the caustic liquid has been completely converted into the carbonate. filtered, to separate the precipitated silica This carbonated mixture is or other comp'oundwhich separates therefrom upon concentration of the liquid, and

the filtrate is then evaporated 'to dryness. If there is any deficiency in the flux so recovered from the amount originally employed, it can be supplemented by the addition thereto of the amount required to make up the equivalent of 100 100% purity. If on the other hand it is found that the dried residue of carbonate so" obtained is in excess of the amount of carbonate originally employed, owing to the presence therein of a portion of the potash contained in the feldspar treated, the surplus over the equivalent of the amount originally employed can be reserved for sale, as

such, or for conversion into any desired.

salt by neutralizing with sulfuric or hydrochloric acid or other desired acids,- and the remainder can be employed as above stated in subsequent operations.

The precipitate obtained after filtering ofl the caustic liquid from the lixiviated and boiled mixture, which precipitate consists apparently of an acid-soluble silicate easily decomposed by boiling with strong mineral acids,is preferably boiled with sufiicient concentrated sulfuric or hydrochloric acid to slightly acidify the mixture, and then,

after digesting at a boiling temperature for a short period, the same is highly diluted and neutralized either with a portion of the clear alkali liquid reservedfor'the purpose, or with a small amount of ammonia, so that the mixture is just a trifle alkaline This causes complete precipitation of the alumina and silica. Accordingly the solution is then filtered and the filtrate will contain substan-;

tially all of the remainder of the original potash in the feldspar in the form of a salt corresponding to the acid employed The filtrate is then slightly acidified in order to facilitate crystallization, and if necessary evaporated to dryness to render any dissolvedsilica insoluble, and-then the liquid 'is concentrated and allowed to crystallize,

. or if the same has contained silica as aforesaid, the residue is taken up with a small amount of a strong acid referably, then diluted with water, and ltered and the filtrate concentrated and allowed to crystallze.

The alumina contained in the precipitate as aforesaid, which is combined with precipitated silica, but apparently exists merely in physical combination therewith and not chemically united therewith, is obtained from this mixture by dissolving the same with the necessary amount of hydrochloric acid required to satisfy the alumina radical,

6., corresponding to the formula The solution so obtained is filtered and the filtrate evaporated to dryness to render parts of flux of' any possible dissolved silica insoluble, and

the residue is taken up with astrong hydrochloric acid, then diluted with water and filtered to remove such insoluble silica Then this practically pure aluminum chlo-' rid is evaporated to dryness andin both in-' stances the vapors of hydrochloric acid evolved in the evaporation of such alumi num chlorid are recovered 'in any suitable manner. The dry residue is then heated in a current of steam, preferably between a dull red and a bright red or yellow heat, but in any event to .a sufiiciently high temperature to completely decompose this aluminum chlorid into aluminum oxid and hydrochloric acid vapors. The vapors aforesaid of hydrochloric acid which are evolved are recovered for use in a subsequent operation.

This decomposition is found to be equally sulfate or preferably with potash alum until the solution is just slightly acidified. The alum is preferablyobtained by the sultable treatment of alunite in the well known manner for example, as described on pp.

159 61 of- Bulletin 551 relating to 'alunite published, 1912 by the U. S. Geological Survey. In this manner it is possible to utilize large quantities-of alum which would otherwise be practically unsalable; After boiling the acidified mixture so obtained the same is neutralized in themanner previously described until the same is just a trifle alkaline, and then the mixture is filtered as previously described and the filtrate containing potassium sulfate is acidified, concentrated and allowed to crystallize. Obviously, if desired, the amount of alum added may be insufiicient to completely neutralize the alkali and the same may be supplemented by the addition of a strong mineral acid 10h as sulfuric acid, until the solution is clearly acid, as shown by suitable tests. The precipitate containing alumina andsilica, is treated as previously described to recover the aluminum as oxid or sulfate of aluminum is recovered if preferred.

Preferably-the fusion when conducted in large masses is continued until every portion thereof has been treated sufiiciently long to admit of the flux reacting with the 'ossible to traliz ing this surplus alkali with aluminum caused to play thereon. Under many conditions of operation, I may employ a gas or fuel-oil furnace, although, as stated, if water power is available the electric type of] furnace, and preferablythe so-called radiant type of electric furnace, is preferably employed.

In'order to clearly complete the decomposition, and I do not restrict my invention as hereinafter claimed to the use of at least this 100% of pearl-ash, the fusion is prefera ly carried out in a furnace in which the bed of the same is maintained as hot, and preferably hotter than the portions ofthe furnace above the layer-ofthe mineral when -on;sa id bed, as otherwise, owing to the relatively poor heat conductivity of feldspar mixture the necessary. degree of fusion is difficult to obtain unless the material is rapidly 'turned over by mechanical means or otherwise. If. Water power is available I prefer'to employ an electric furnace having preferably carbon electrodes, and preferably an alternating current, although a direct current or if desired suitable metal electrodes may be employed, as the temperatureat which the fusion occurs is sulficiently low, not exceeding 1200 C. to preclude any possibility of electrolysis of the material treated.

The invention as herein described obviously covers the employment of various alkali metal bearing silicates and alunite or similar materials, and the claims are intentionally drawn to cover in their broadest aspect the various equivalents which they may properly be construed to include.

While it is preferable to maintain as low a temperature in the furnace as is compatible with efiective decomposition, it is obvious that if any of the materials treated are volatilized thesame may be recovered by suitable dust collectors-arranged in the outlet flue of the furnace. The material so recovered may be treated to recover the otassium compounds or other. valuable pro ucts contained therein.

While'preferably I employ 100% of flux any amount in excess of 25% by weight of the-mineral treated and-less than 200% maybe employed, provided the amount is suflicient to accomplish the incipient fusion. and

effective decomposition and destruction of the identity of the original feldspar.

Having thus described my invention, what I claim and desire to secure by Letters Patent is n y 1. In the decomposition of alkali, alumi num-bearing silicates,the steps which consist in reacting upon refractory, potash-bearing, silicious, aluminiferous minerals in order to recover the alkali, alumina and silica separately therefrom, with a .suflicient amount of an alkali flux and at least 40% by weight to materially decompose the mixture and at a temperature sufliciently high to effect at least incipient fusion thereof; then decomposingv the resultant'mass with water, removing-the precipitate obtained, then decomposing the said precipitate with a compound having an acid reaction, then filteri-ngthe mixture so obtained while in such a condition as to effect the precipitation of substantially all ofv the silicon and aluminum compounds simultaneously, then recovering a compound of potassium from the filtrate. 2. In the process of obtaining potash from native minerals, the steps which consist in reacting upon the products, obtained by fusion of potash feldspar with a large amount of an alkaline fiux sufficient to effect substantially complete decomposition thereof and a subsequent lixiviation thereof with Water, with suflicient alum-containing material to substantially decompose the said product and neutralize the excess of alkali,

' and then separating the aluminum compounds and the silicon compounds simultaneously from aid mixture by filtering the same while in a substantially neutral condition.

3. In the process of recovering potash, the steps which consist in treating the product obtained by the fusion of potash feldspar with relatively large amounts of an alkali flux from 40% to 175%. by weight and a subsequent lixiviation thereof with water and then adding sufiicient aluminum-sulfate-containing solution to substantially neutralize the surplus alkali; then rendering the mixture sufliciently neutral to' effect the precipitation of substantially all. of the alumina and silica therein. I 4. In the decomposition of potash-bearing silicates the process which consists in reacting upon refractory, potash-bearing, silicious minerals with a suflicient amount of an alkali flux and at a sufiiciently high temperature to materially decompose said mixture into acid-soluble, potassium silicate and silica; then lixiviatin said mixture with water,

removing 'the-inso uble matter, then decomposing said insoluble matter with a [compound having an acid reaction, then filtering said resulting mixture while substantially neutral and in such, a conditionas to efi'ect 5. In the decomposition of alkali-bearing silicates containing relatively large percentage of silica and alumina, the process which consists in reacting upon refractory, potash-bearing silicious minerals with a suf- -ficient amount of potash flux, at least by weight, and at a sufficiently high temperature, to materially decompose said mixture into acid-soluble, potassiumsilicate and silica; then lixivating said mixture with water, removing the precipitate obtained, then decomposing said precipitate with a compound having an acid reaction, then filtering said .resulting mixture while substantially neutral and in such a condition as to effect the precipitation simultaneously of silica and alumina, and then recovering the, potassium compound from the filtrate.

6. In the process of treating potash-bearingfeldspar, the steps which consist in adding an acid to a strong alkaline solution containing alumina and silica, and then filtering said solution While sufficiently approaching its neutral point to permit of the separation of substantially all of the alumina and a large part of the silica by simultaneous precipitation thereof.

7. The process of treating refractory potash-bearing silicious minerals in order to recover the alkali and alumina separately therefrom, which consists in first finely subdividing the same and fusing with'an alkalimetal flux in excess of 40% and less than 200% -'by weight of the mineral treated, for a sufiicient period and at a sufliciently high temperature to eflect substantial decomposition of said mineral, then digesting said mass in a finely divided condition in an aqueous solution and at an elevated temperature, then separating the insoluble material from said resultant mixture and rendering the same substantially neutral but still slightly alkaline, then filtering. off the insoluble precipitate and then recovering the potassium salt from'the" resulting filtrate.

8. In the process of treating feldspar, the steps which consist in fusing the same with an alkali-metal flux in excessof 40% and less than 200% by Weight of the mineral treated, andthen recovering a potassium compound from the decomposed mass by subjecting the water-insoluble portion of the same to a secondary decomposition with an acid in an amount sufficient to satisfy the alkali-metal oxid radical of any alkali-metal compound contained in said mass andinsufiicient to materially satisfy the aluminum oxid radical of any aluminum compound contained in said mass, then separating the insoluble precipitate thereby produced and treating the filtrate to obtain the resultant potassium salt.

potash-bearing feldspar in order to recover the potash and alumina separately therefrom, the steps which consist in heating said tion with from 7 5% to 125%, by weight of the mineral treated, of a water-soluble, alkaline, oxygen compound of an alkali-metal for a suflicient period and at a sufficiently high temperature, not less than a bright red heat, to effect substantial decomposition of said mineral while in a finely subdivided condimineral and to thereby render the potash and alumina contained therein soluble in a mineral acid, removing the heated mass from the influence of said heat, digesting the resultant mass with a relatively large volume of water for a suflicient time to dissolve the water-soluble alkali compounds there-- from, and then filtering off the water-insoluble alkali compounds.

In witness whereof I have hereunto set my hand at the city, county and State of New York, this 22nd day of March, 1912.

WAITSTILL H. SWENARTON.

Witnessesi CLARENCE J. Wrcxorr, LIE. JOHNSTON. 

